Phased antenna arrays provide beamforming and beam-steering capabilities by controlling the relative phases of electrical signals applied across antenna elements of the array. The two most common types of phased antenna arrays are continuous phased arrays and binary phased arrays.
Continuous phased arrays use analog phase shifters that can be adjusted to provide any desired phase shift in order to steer a beam towards any direction in a beam scanning pattern. However, continuous phased arrays are typically either lossy or expensive. For example, most continuous phase shifters are based on varactor-tapped delay lines using variable capacitive and/or variable inductance elements. Variable capacitive elements, such as varactor diodes and ferroelectric capacitors, are inherently lossy due to resistive constituents or poor quality in the microwave region. Variable inductance elements, such as ferromagnetic devices, are bulky, costly and require large drive currents.
Binary phased arrays use phase shifters capable of providing two different phase shifts of opposite polarity (e.g., 0 and 180°). Binary phase shifters are typically implemented using diode or transistor switches that either open/short the antenna element to ground or upshift/downshift the antenna element's resonant frequency. Diode switches are most commonly used in narrowband applications with small antenna arrays. However, in large antenna arrays, transistors are generally preferred due to the excessive dc and switching currents required to switch a large number of diodes. For broadband applications, high-frequency, high-performance field effect transistor (FET's) are required, which substantially increases the cost of the binary phase shifter. For example, the current cost of a 5-GHz FET is usually around $0.20-$0.30, whereas the current cost of a 20-30 GHz FET is upwards of $5.00.
Therefore, what is needed is a cost-effective binary phase-shifting mechanism for broadband antenna arrays.